Load responsive hydraulic system

ABSTRACT

Each directional control valve of a load responsive hydraulic system supplies a flow of signal fluid to a work port channel thereof and pressurizes this flow of signal fluid to a predetermined pressure magnitude above the load actuating pressure in the work port channel to provide a synthetic signal pressure. Fluid logic is provided for the selection of the highest synthetic signal pressure from any of the directional control valves and for application of this highest synthetic signal pressure to an effective output operator for the control of the pressure and effective output of the pump.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to directional control valves ofthe type in which the load actuating pressure of a fluid motor is sensedby the directional control valve when the directional control valve issupplying pressurized fluid from a pressure inlet channel to a work portchannel.

The present invention also generally relates to load responsivehydraulic systems of the type in which the pressure and the effectiveoutput of the pump are controlled to maintain the system pressure at apredetermined pressure magnitude above the highest load actuatingpressure that exists in a plurality of directional control valves. Thecontrol of the pressure and effective output of a variable displacementpump is achieved by the control of the pump displacement; and thecontrol of the pressure and the effective output of a fixed displacementpump is achieved by a by-pass valve that discharges excess pump flow toa sump.

The present invention more particularly relates to load responsivehydraulic systems of the type in which a flow of signal fluid issupplied from the pump and this flow of signal fluid is used to generatea synthetic signal pressure that is higher than the highest loadactuating pressure that exists in a plurality of directional controlvalves.

The present invention specifically relates to load responsive hydrauliccontrol valves in which each directional control valve furnishes a flowof signal fluid from the pressure inlet channel thereof to the work portchannel thereof, and in which a synthetic signal pressure is generatedin this flow path from the pressure inlet channel to the work portchannel.

The present invention also specifically relates to load responsivehydraulic systems in which a plurality of directional control valves,each providing their own supply of signal fluid only when needed, areinterconnected to form a load responsive hydraulic system in which themaximum flow capacity of each directional control valve is increased bythe control of the pressure and effective output of the pump by thehighest synthetic signal pressure, and in which all shock pressureproblems relating to the flow of signal fluids are eliminated by thesignal fluid being furnished to each directional control valve only whenneeded.

2. Description of the Prior Art

The use of a pump supplied fluid for the generation of synthetic signalpressure in load responsive hydraulic systems was disclosed in U.S. Pat.No. 3,971,216 of common inventor entity and common assignee. Thesynthetic signal pressure that is developed therein is a predeterminedvalue above the highest load actuating pressure of any of thedirectional control valves that are supplying pressurized fluid to afluid motor. By controlling the effective output of the pump by thissynthetic signal pressure, the pressure differential across adirectional control valve, from a pressure inlet channel to the workport channel, is increased and therefore the maximum flow capacity ofthe directional control valve is increased.

The above referenced load responsive hydraulic system, of the syntheticsignal type, achieves the advantage of a low stand-by pressure for theminimization of power loss and heat rise during stand-by conditions andalso achieves the additional advantage of a relatively high differentialpressure, from a pressure inlet channel to a respective work portchannel of any of the directional control valves, for achieving goodflow capacity to the work port channels. However, the synthetic signaltype of load responsive hydraulic system has the inherent disadvantageof producing pressure surges in the output pressure due to the flow ofsignal fluid and resultant timing problems in the individual directionalcontrol valve.

Schurger, in U.S. Pat. No. 3,878,864, disclosed a load responsivehydraulic system in which a signal fluid was supplied from the pump anda unique by-pass valve to the directional control valve only after theload actuating pressure from one of the control valves was supplied tothe special and rather complex by-pass valve. The use of this by-passvalve was effective to start the flow of signal fluid only when neededand thus eliminated shock pressures which ordinarily would occur in aload responsive system of the synthetic signal type when a directionalcontrol valve is moved from a stand-by position to an operatingposition; but it was not effective to stop the flow of fluid before anunnecessarily high shock peak was developed when the directional controlvalve was moved from the operating position back to a stand-by position.

In this same patent, Schurger disclosed a load responsive control valvewhich, when used in conjunction with his specially designed by-passvalve, would eliminate the shock peak that ordinarily would be incurredwhen the valve spool of the directional control valve were moved from anoperating position back to a stand-by position.

In U.S. Pat. No. 4,089,169 of common inventor entity and common assigneeas that of the present invention, a load responsive hydraulic system isdisclosed that includes a logic system that is effective to control theflow of signal fluid to the load responsive directional control valvesonly after an attenuation flow path in one of the directional controlvalves is occluded. This unique logic system is effective to solve, withless complexity and lower cost than the Schurger by-pass valve, theshock pressure peaks which are associated with moving a valve spool ofthe directional control valve from stand-by position to an operatingposition; and, when used in a load responsive system having directionalcontrol valves similar to those that are disclosed by Schurger, iseffective to eliminate all shock pressure problems which are associatedwith load responsive hydraulic systems of the synthetic signal type.

In the FIG. 3 embodiment of U.S. Pat. No. 3,971,216, a directionalcontrol valve was disclosed in which the synthetic signal fluid isfurnished from either of a pair of pressure inlet channels of adirectional control valve to a control port of the directional controlvalve by a pair of valved flow paths. This FIG. 3 embodiment is similarto the present invention in that a valved signal path was provided; butit differs in that no provision was made to time the opening and theclosing of these valved signal paths with the opening and closing of thefluid flow paths between the respective ones of the work port channelsand the return channels.

SUMMARY OF THE INVENTION The Basic Directional Control Valve

The basic directional control valve includes a valve body having apressure inlet channel, first and second work port channels, and areturn channel. A valve spool is slidably inserted into the valve bodyand is movable from a stand-by position to an operating position toestablish a first fluid flow path from the pressure inlet channel to thefirst work port channel and to establish a second fluid flow path fromthe second work port channel to the return channel.

The directional control valve also includes cooperating portions of thevalve spool and the valve body which are effective to establish arestricted flow path from the pressure inlet channel to the first workport channel after the second fluid flow path is established, therebyproviding a limited flow of signal fluid from the pressure inlet channelto the first work port channel only after fluid can be exhausted fromthe second work port channel to the return channel by the fluid motor.In other words, the flow of signal fluid is supplied only when this flowof signal fluid can actuate the fluid motor by fluid flow into one portthereof with resultant exhaust flow out of the other port thereof.

In a preferred embodiment, a second fluid restrictor is placed into therestricted flow path and the pressure intermediate of the tworestrictions, which is at a predetermined pressure magnitude above theload actuating pressure of the fluid motor and which is called thesynthetic signal pressure, is sensed for application to an effectiveoutput operator that controls the pressure and effective output of ahydraulic pump.

Optional Valve Configurations

In several optional configurations of the present invention, the flow ofsignal fluid which is supplied by the directional control valve flowsthrough a check valve or other one-way flow means directly to a workport channel of the directional control valve rather than beingcontrolled by the valve spool. In these optional configurations, thevalved signal principle and function of the present invention may beadapted to directional control valves which include flow control devicesintermediate of the valve spool and the work port thereof, such as thecopending application of common inventor entity, common assignee, andcommon filing date.

Logic System for the Interconnection of Directional Control Valves

All of the embodiments for the directional control valves for thepresent invention may be interconnected by the use of series connectedthree-port logic valves such as are fully shown and described in U.S.Pat. No. 3,971,216; or because of the change in the direction in theflow of signal fluid in the present invention from that of the syntheticsignal system in U.S. Pat. No. 3,971,216, a simpler and lower cost logicsystem, which comprises parallel connected check valves, may be used.

OBJECTS OF THE INVENTION

It is a first object of the present invention to provide a loadresponsive hydraulic system of the synthetic signal type in which shockpressures are minimized during the actuating of the directional controlvalve from a stand-by position to an operating position.

It is a second object of the present invention to provide a loadresponsive hydraulic system of the synthetic signal type in which shockpressures are minimized during the actuating of the directional controlvalve from the operating position to the stand-by position.

It is a third object of the present invention to provide a loadresponsive hydraulic system in which signal fluid is furnished to eachdirectional control valve only when needed.

It is a fourth object of the present invention to provide a loadresponsive hydraulic system in which signal fluid is furnished to eachdirectional control valve from the pressure inlet channel thereof.

It is a fifth object of the present invention to provide a restrictedflow path from the pressure inlet channel to the work port channel whenthe pressure inlet channel is communicated to the work port channel forthe supply of pressurized fluid to a fluid motor.

It is a sixth object of the present invention to provide a directionalcontrol valve in which a restricted flow path is established from thepressure inlet channel to the first work port channel after a fluid flowpath has been established from the second work port channel to thereturn port channel.

It is a seventh object of the present invention to provide a directionalcontrol valve in which a signal flow path, having first and second fluidrestrictors connected in series therein, is established from thepressure inlet channel to the work port channel of the directionalcontrol valve when a fluid flow path is established from the pressureinlet channel to the work port channel for the supplying of pressurizedfluid to a fluid actuated device, and in which a synthetic signalpressure is sensed intermediate of the series-connected restrictor.

It is an eighth object of the present invention to provide a directionalcontrol valve in which a signal flow path, having first and secondseries-connected fluid restrictors therein, is established from thepressure inlet channel to the first work port channel after a fluid flowpath has been established from a second work port channel to a returnport channel, and in which a synthetic signal pressure is sensedintermediate of the series-connected restrictors.

It is a ninth object of the present invention to provide a directionalcontrol valve which includes a valved flow path portion from thepressure inlet channel to a control port thereof.

It is a tenth object of the present invention to provide a directionalcontrol valve which includes a first valved flow path portion from thepressure inlet channel to a control port and a second valved flow pathportion from the control port to the work port channel.

It is an eleventh object of the present invention to provide adirectional control valve which includes a valved flow path portion fromthe pressure inlet channel to a control port and which includes one-wayflow means from the control port to a work port channel.

It is a twelfth object of the present invention to provide a loadresponsive hydraulic system in which the logic system thereof includesseries-connected three-port logic valves that interconnect the syntheticsignal pressures of the individual directional control valves and thatselect the highest synthetic signal pressure therefrom for control ofthe pressure and effective output of the pump.

It is a thirteenth object of the present invention to provide a loadresponsive hydraulic system in which the logic system thereof includesparallel-connected check valves that interconnect the synthetic signalpressures of the individual directional control valves and that selectthe highest synthetic signal pressure therefrom for control of thepressure and effective output of the pump.

These and other objects will be apparent to the reader from the detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional drawing of a first preferred embodiment of adirectional control valve of the present invention, with the valve spoolthereof in the stand-by position;

FIG. 1A is a partial and phantom cross-sectional view showing a valvespool modification of the directional control valve of FIG. 1;

FIG. 3 is a cross-sectional drawing of the directional control valve ofFIG. 1 taken substantially as shown by cross-section line 2--2 of FIG.1;

FIG. 3 is a schematic drawing of typical hydraulic system componentswhich may be used with any of the directional control valves of thepresent invention;

FIG. 4 is a front view of the valve spool of the directional controlvalve of FIG. 1, taken substantially as shown in FIG. 1;

FIG. 5 is a top view of the valve spool of FIG. 4 taken substantially asshown by view line 5--5 of FIG. 4;

FIG. 6 is a cross-sectional view of the valve spool of FIG. 5 takensubstantially as shown by section line 6--6 of FIG. 5;

FIG. 7 is a cross-sectional view of the valve spool of FIG. 5, takensubstantially as shown by section line 7--7 of FIG. 5;

FIG. 8 is a partial cross-sectional view of the directional controlvalve of FIG. 1, taken substantially as shown in FIG. 1 but with thevalve spool thereof moved to an operating position;

FIG. 9 is a partial cross-sectional view of the directional controlvalve of FIG. 8, taken substantially as shown by section line 9--9 ofFIG. 8;

FIG. 10 is a partial cross-sectional view of the directional controlvalve of FIG. 1, showing a detail thereof in an enlarged scale;

FIG. 11 is a partial cross-sectional view of the directional controlvalve of FIG. 1 taken substantially as shown by section line 11--11 ofFIG. 10;

FIG. 12 is a schematic drawing of typical system components which may beused with any of the directional control valves of the present inventionand which may be used alternately with the system components of FIG. 3;

FIG. 13A is a schematic drawing of parallel-connected logic forinterconnecting the valved signal means of FIGS. 13B-13C;

FIG. 13B is a schematic drawing for a valved signal means of adirectional control valve, being adapted for use with theparallel-connected logic of FIG. 13A;

FIG. 13C is a schematic drawing of a different valved signal means foruse with the logic of FIG. 13A;

FIG. 13D is a schematic drawing of a third variation of a valved signalmeans;

FIG. 14A is a schematic drawing of series-connected logic forinterconnecting the valved signal means of FIGS. 14B-14E.

FIG. 14B is a schematic drawing of a valved signal means of adirectional control valve, being adapted for use with theseries-connected logic of FIG. 14A, but also being usable with theparallel-connected logic of FIG. 13A;

FIG. 14C is a schematic of a different valved signal means for use withthe logic of FIG. 14A;

FIG. 14D is a schematic of a third variation of valved signal means foruse with the logic of FIG. 14A;

FIG. 14E is a schematic of a fourth variation of valved signal means foruse with the logic of FIG. 14A;

FIG. 15 is a partial and phantom cross-sectional drawing of a secondpreferred embodiment of a directional control valve of the presentinvention with cored passages of the valve body thereof outlined andwith the valve spool thereof in the stand-by position;

FIG. 16 is a partial and phantom cross-sectional drawing of thedirectional control valve of FIG. 15 but with the valve spool thereofmoved to a first operating position;

FIG. 17 is a partial and phantom cross-sectional drawing of thedirectional control valve of FIG. 15 but with the valve spool thereofmoved to a second operating position;

FIG. 18 is a partial and phantom cross-sectional drawing of thedirectional control valve of FIG. 15 but with the valve spool thereofmoved to a float and regenerative position; and

FIG. 19 is a partial and phantom cross-sectional drawing of thedirectional control valve of FIGS. 15-18 with a flow control interposedbetween the valve spool and one work port.

DETAILED DESCRIPTION The Fixed Displacement Pump System

Referring now to FIG. 3, a typical schematic circuit and typicalcomponents thereof are shown for utilizing a directional control valveof the present invention in a load responsive hydraulic system whichincludes a fixed displacement pump. The circuitry of FIG. 3 includes asource of pressurized fluid 20 which comprises a pump 22 and a sump 24a,an effective output means or by-pass valve 26 which includes aneffective output operator 28, another operator 30, and a spring 32.

In operation, the pump 22 delivers pressurized fluid to a pump pressureconduit 34 for use by one or more directional control valves of thepresent invention which will be subsequently described, and a signalpressure, which may be either the highest load actuating pressure orsynthetic signal pressure from these control valves, is supplied to asignal conduit 36 and to the effective output operator 28. The operators28 and 30 have equal areas; and the by-pass valve 26 is moved to aposition 38, as shown, when a force that is developed by the signalpressure in the effective output operator 28, plus the force of thespring 32, is greater than the force developed by the pump outputpressure in the operator 30; and the by-pass valve 26 is moved to aposition 40 wherein a flow path 42 by-passes excess fluid from the pump22 to the sump 24a via a conduit 44 when the force of the operator 30exceeds the combined forces of the operator 28 and the spring 32. Thusthe by-pass valve 26 is effective to control the pressure and theeffective output of the pump 22 to maintain a pump pressure in theconduit 34 which exceeds the signal pressure in the signal conduit 36 bya value which is in accordance with the effective area of the operator30 divided by the force of the spring 32.

The Variable Displacement Pump System

Referring now to FIG. 12, the variable displacement pump system of FIG.12 includes a source of pressurized fluid 46 having a variabledisplacement pump 48 and having a sump 24b, a displacement control pilotvalve 52 that includes a spring 54 and that also includes both aneffective output operator 56 and another operator 57, a pilot reliefvalve 58, and a sump 24c. The pump 48 includes a displacement controloperator 50 which is effective to decrease the displacement of the pump48 in response to fluid pressure supplied to the operator 50, and aspring 49 which is effective to incresse the displacement of the pump 48in the absence of a spring overcoming force from the displacementcontrol operator 50.

Thus the system of FIG. 12 includes effective output means 60 whichcomprises both the displacement control operator 50 of the variabledisplacement pump 48 and the displacement control pilot valve 52 withthe effective output operator 56 thereof.

In operation, either the load actuating pressure of a directionalcontrol valve or a synthetic signal pressure from a directional controlvalve, is applied to a signal conduit 36. When the signal pressure ofthe signal conduit 36 creates a fluid force in the effective outputoperator 56 which, together with the force of the spring 54, iseffective to overcome the pressure of the pump 48 in the operator 57,then the pilot valve 52 is moved to a position 64 wherein a flow path 66communicates the displacement control operator 50 with the sump 24callowing the spring 49 of the pump 48 to actuate the pump 48 to a higherdisplacement by exhausting fluid from the displacement control operator50 to the sump 24c via the flow path 66.

When the pump pressure in the operator 57 is effective to overcome thecombined force of the effective output operator 56 and the spring 54,the pilot valve 52 is actuated to a position 68 wherein a flow path 70adds pressurized fluid to the displacement control operator 50 from thepump pressure conduit 34; and the displacement control operator 50reduces the displacement of the pump 48 in opposition to the force ofthe spring 49.

The pilot relief valve 58 is effective to limit the maximum fluidpressure in the signal conduit 36; so that the maximum output pressureof the pump 48 is a function of the pressure setting of the pilot reliefvalve 58 and the load of the spring 54. This use of a pilot relief valveis standard in the art for controlling the maximum operating pressure ofvariable displacement pumps, such as the pump 48, and for controllingthe maximum operating pressure of fixed displacement pumps, such as thepump 22 of the FIG. 3 system embodiment.

A First Preferred Valve Embodiment

Referring now to FIGS. 1 and 2, a directional control valve 80 includesa valve body 82 having a spool bore 84, having first and second workport channels 86 and 86b, having a return port means 88 that includes afirst return channel 90a and a second return channel 90b, and having apressure inlet channel 92. A valve spool or movable valving element 94is slidably inserted into the spool bore 84 and is positionable to astand-by position as shown in FIGS. 1 and 2 and to an operating positionas shown in FIGS. 8 and 9.

Referring now to FIGS. 4 and 5, the valve spool 94 includes a first landportion 96, a second land portion 98, a center land portion 100, a firstreduced cross-section portion 102, a second reduced cross-sectionportion 104, diametrically opposed and longitudinally extending grooves106a and 106b in the center land portion 100, tang and notch means 108aand tang and notch means 108b that are disposed on opposite ends of thecenter land portion 100 and that include longitudinally extending tangs110a and 110b, radial balancing holes 112a and 112b that are generallydisposed in respective ones of the tangs 110a and 110b, outlet meteringnotches 114a and 114b and outlet metering notches 116a and 116b.

Tang and notch means 108a comprises diametrically opposed tang notches118a and 118b and metering notches 120a and 120b; and, in like manner,tang and notch means 108b comprises diametrically opposed tang notches122a and 122b and metering notches 124a and 124b. The valve spool 94also includes circumferential groove 126.

Referring now to FIGS. 1, 1A, and 2, the directional control valve 80includes valved signal means 128 which comprises a control port 130, aconnecting passage 132 that communicates with the control port 130, afirst signal passage 134a and a second signal passage 134b that bothcommunicate with the connecting passage 132, signal or attenuationpassage 135, bore groove 136, orifice plates 137a and 137b whichrespectively include fixed conductance restrictors 138a and 138b,one-way flow and reverse flow restrictor valves 140a and 140b whichrespectively include seats 142a and 142b and balls 144a and 144b, seatgrooves or fixed conductance restrictors 146a and 146b, and cooperatingportions of the valve spool 94.

The cooperating portions of the valve spool 94 which are included in thevalved signal means 128 include the center land portion 100, tangs 110aand 110b of the center land portion 100, longitudinally extendinggrooves 106a and 106b of the center land portion 100, the reducedcross-section portions 102 and 104, the second land portion 98, thecircumferential groove 126, and another land portion 148.

Referring now to FIGS. 4 to 7, FIG. 6 shows the substantially constantcross-sectional areas of the longitudinally extending grooves 106a and106b; and FIG. 7 shows a cross-sectional area of the center land portion100 through the tang 110b thereof and also shows an end view of themetering notches 124a and 124b. As shown in FIG. 7, the tang 110bincludes cylindrical surface portions 150a and 150b.

Referring now to FIGS. 10 and 11, FIG. 10 shows an enlarged portion ofFIG. 1, taken substantially as shown in FIG. 1, and depicting the seat142a and the seat groove or fixed conductance restrictor 146; and FIG.11 shows a top view of the seat 142a and the restrictor 146a. The seat142b and the fixed conductance restrictor 146b are the same as the seat142a and groove 146a of FIGS. 10 and 11.

Referring now to FIGS. 1 to 3, the directional control valve 80 istypical of one of a number of working sections of a sectional typedirectional control valve which may be bolted together at faces 152a and152b by a plurality of bolts (not shown) which are inserted through aplurality of holes 154. Each working section, such as the directionalcontrol valve 80, may then be connected to a fluid actuated device suchas the fluid actuated device 156 which is connected to the work portchannels 86a and 86b by actuating ports 158a and 158b respectively. Thepump pressure conduit 34 of the FIG. 3 illustration is then connected tothe like numbered conduit of FIG. 2 to supply pressurized fluid to thepressure inlet channel 92 of the directional control valve 80 and to anyother working sections that may be included.

In stand-by operation, with the valve spool 94 in the stand-by positionas shown, the pressure inlet channel 92 is isolated from the work portchannels 86a and 86b; and the work port channels 86a and 86b areisolated from the return port means 88 which includes the returnchannels 90a and 90b. Also, at this time, the signal passages 134a and134b are isolated from both the pressure inlet channel 92 and fromrespective ones of the work port channels 86a and 86b by the center landportion 100; so the load actuating pressures in the work port channels86a and 86b are not sensed by the control port 130.

Instead, at this time, the control port 130 is communicated to thereturn channel 90b by the signal or attenuation passage 135 and the boregroove 136 which cooperate with the circumferential groove 126 toprovide a fluid flow path or attenuation flow path 160 from the controlport 130 to the second return channel 90b. The attenuation flow path 160is effective to attenuate or reduce the signal pressure in the signalconduit 36 to the value of the pressure in a sump 24e; so that a verylow pressure of the pump 22 in the operator 30 is effective to overcomethe spring 32, thereby moving the by-pass valve 26 to the position 40and by-passing all of the fluid of the pump 22 to the sump 24a via theflow path 42.

Referring now to FIGS. 1-3 and 8-9, the valve spool 94 of FIGS. 8 and 9has been moved to an operating position wherein a first fluid flow path162 has been established from the pressure inlet channel 92 to the firstwork port channel 86a; and wherein a second fluid flow path 164 has beenestablished from the second work port channel 86b to the second returnchannel 90b; so that pressurized fluid is supplied from the pump 22 ofFIG. 3 to the fluid actuated device 156 of FIG. 1 via the firstactuating port 158a, and fluid is exhausted from the fluid actuateddevice 156 through the second actuating port 158b.

At this time, a third fluid path or restricted flow path 166 isestablished from the pressure inlet channel 92 to the first work portchannel 86a. The restricted flow path 166 includes a valved orrestricted flow path portion 168 and a valved or restricted flow pathportion 170 that are interconnected by the connecting passage 132. Thevalved or restricted flow path portion 168 includes the grooves 106a and106b, signal passage 134b, and the restrictor 138b in the signal passage134b. The valved or restriced flow path portion 170 includes the signalpassage 134a, the restrictor 138a in the signal passage 134a, and thegroove or restrictor 146a in the signal passage 134a. The valved orrestricted flow path portion 170 is valved by the interaction of thetang 110a and the reduced cross-section portion 102 with the signalpassage 134a; and the valved or restricted flow path portion 168 isvalved by interaction of the center land portion 100 and the grooves106a and 106b thereof with the signal passage 134b.

With the pressure inlet channel 92 of the directional control valve 80being connected to the pump 22 by the pump pressure conduit 34, and withthe valve spool 94 being in the operating position as shown in FIGS. 8and 9, a supply of signal fluid is furnished from the pressure inletchannel 92 to the first work port channel 86a by the third fluid flowpath 166. This flow of signal fluid flows through the fixed conductancerestrictor 138b to reach the connecting passage 132 and then through theseries-connected restrictors 138a and 146a to reach the first work portchannel 86a. Thus this signal fluid flows through a single fluidrestrictor 138b to reach the connecting passage 132 and through twoseries-connected restrictors, 138a and 146a, to flow from the connectingpassage 132 to the work port channel 86a.

If all three of the restrictors in the third fluid flow path 166 havethe same conductance, then not only is the flow through each of thesefluid restrictors at the same flow rate, but also the pressure dropacross each fluid restrictor will be the same. Therefore, the fluidpressure in the connecting passage 132, and thus in the control port 130will be less than the fluid pressure in pressure inlet channel 92 byone-third of the difference between the fluid pressures in pressureinlet channel 92 and the first work port channel 86a. Also, the pressuredifferential between the pressure inlet channel 92 and the control port130 will correspond to the area of the operator 30 of the by-pass valve26 divided by the spring load of the spring 32.

The result of the combination thus described is that the pump operatingpressure will be maintained at a first predetermined pressure magnitudeabove the fluid pressure in the signal conduit 36 and in the controlport 130 by virtue of the spring 32; and the pressure magnitude of thepump 22 will be maintained at two additional and equal pressuremagnitudes above the pressure magnitude of the load actuating pressurein the work port channel 86a by virtue of the pressure differentialsacross both the fixed conductance restrictor 138a and the fixedconductance restrictor 146a.

Or, in other words, during stand-by conditions, the pressure of the pump22 will be maintained at a pressure differential above the fluidpressure in the sump 24d in accordance with the force magnitude of thespring 32; and when the valve spool 94 is in the operating position asshown in FIGS. 8 and 9, the pressure of the pump 22 will be maintainedat a pressure magnitude above the load actuating pressure in the workport channel 86a which is three times the quotient of the area ofoperator 30 divided by the force of the spring 32. This higher pressuredifferential between the pump 22 and the load actuating pressure in thework port channel 86a is effective to increase the flow capacity of thedirectional control valve 80 by 73% by tripling the pressuredifferential from the pressure inlet channel 92 to the first work portchannel 86a via the first fluid flow path 162.

In order to avoid shock pressure surges, which would be caused byblocking the flow of signal fluid and thereby allowing the pressuremagnitude of the signal pressure to equal that of the pressure inletchannel 92, the second fluid flow path 164 must be opened before thethird fluid flow path 166 is established; and the third fluid flow path166 must be occluded before the second fluid flow path 164 is occluded.

If the third fluid flow path 166 is considered to include both the flowpath portion 168 which includes and is valved by the longitudinallyextending grooves 106a and 106b and the flow path portion 170 whichincludes and is valved by interaction of the first signal passage 134aand the tang 110a, then the flow path portion 170 must be opened beforethe flow path portion 168 is opened and the flow path portion 168 mustbe closed before the flow path portion 170 is closed.

In addition, the attenuation flow path 160 must be closed before theflow path portion 170 is opened or pressurized fluid will be lost fromthe first work port channel 86a to the sump 24d; and the attenuationflow path 160 must also be closed before the flow path portion 168 isopened or pressurized fluid will be lost from the pressure inlet channel92 to the sump 24e.

The timing of the opening of the first fluid flow path 162 with respectto the opening of the flow path portions 168 and 170 is not particularlyimportant; except that, it is preferable to open the flow path portions168 and 170 before opening the first fluid flow path 162 so that thepressure of the pump 22 is adjusted in accordance with the loadactuating pressure in the first work port channel 86a before the fluidflow path 162 is established, and thereby any delay in system responseis avoided.

Referring again to FIGS. 1-2 and 8-9, the timing of the valve spool 94with respect to the various channels in the valve body 82 preferablyprovides the following sequence of fluid communications and occlusionsas the valve spool 94 is moved from the stand-by position in FIGS. 1 and2 to the first operating position of FIGS. 8 and 9: occlusion of theattenuation flow path 160 and establishing of the second fluid flow path164 from the second work port channel 86b to the return channel 90b,opening the flow path portion 170 from the control port 130 and theconnecting passage 132 to the first work port channel 86a, opening theflow path portion 168 from the pressure inlet channel 92 to the controlport 130 and to the connecting passage 132, and opening the first fluidflow path 162 from the pressure inlet channel 92 to the first work portchannel 86a.

As the valve spool 94 is actuated from the operating position of FIGS. 8and 9 to the stand-by position of FIGS. 1 and 2, the sequence ofoccluding and establishing fluid flow paths will be the opposite of thatwhich has been recited above for actuating of the valve spool 94 fromthe stand-by position to the operating position. The actual distance ofmovement of the valve spool which is required between each establishingand occluding of each flow path will be in accordance with themanufacturing accuracy which can be maintained; and the illustrations ofFIGS. 1 and 2 and of FIGS. 8 and 9 are drawn to approximate theaforementioned timing relationships.

Referring again to FIGS. 1, 2, 8, and 9, if the valve spool 94 is movedto the left of the stand-by position of FIGS. 1 and 2 to a secondoperating position, in like manner as the valve spool 94 is moved to theright in FIGS. 8 and 9 to a first operating position, then a fluid flowpath 163 will be established from the pressure inlet channel 92 to thework port channel 86b, another fluid flow path 165 will be establishedfrom the work port channel 86a to the return channel 90a and to a sump24e, and another fluid flow path or restricted flow path 167 will beestablished from the pressure inlet channel 92 to the work port channel86b.

The restricted flow path 167 will include the valved or restricted flowpath portions 169 and 171 which are interconnected by the passage 132.The flow path portion 169 will be valved by the longitudinal grooves106a and 106b and will include the signal passage 134a and therestrictor 138a therein; and the flow path portion 171 will be valved byboth the tang 110b and the reduced cross-section portion 104 and willinclude the signal passages 134b and the restrictors 138b and 146b.

Thus, in the second operating position, one-way flow and reverse flowrestrictor valve 140a provides free flow from the longitudinal grooves106a and 106b to the restrictor 138a, and the one-way flow and reverseflow restrictor valve 140b provides a fluid restriction intermediate ofthe restrictor 138b and the work port channel 86b.

System with Parallel Logic

Referring now to FIGS. 13A-13D, parallel logic 180, which includes checkvalves 182a and 182b and which also includes attenuation flow path 184,is used to interconnect valved signal means 188, 190, and 192.

The check valves 182a and 182b include respectively flow inlet ports179a and 179b and flow outlet ports 181a and 181b. Any point ofconnection, such as a point 183 to a conduit 189 that interconnects theflow outlet ports 181a and 181b may be considered as a third logic portof the parallel logic 180, and the flow inlet ports 179a and 179b may beconsidered as first and second logic ports, respectively, of theparallel logic 180.

The check valves 182a and 182b are effective to select the higher signalpressure from either of the valved signal means, 188 or 190; becauseeach signal means, 188 or 190, receives its own flow or supply of signalfluid from a pressure inlet channel thereof, as represented by a box198a or 198b, and generates a signal pressure in a control port 130a or130b thereof; and so the higher fluid pressure will be transmitted froma control port, 130a and 130b, to the signal conduit 36 by one of thecheck valves, 182a and 182b.

When the higher signal pressure is decreased, the fluid pressure in thesignal conduit 36 is decreased by the attenuation flow path 184, whichincludes a restrictor 185, to a sump 24f.

In contrast, the highest signal pressure of the load responsive systemof U.S. Pat. No. 3,971,216 cannot be selected by a logic system ofparallel-connected check valves because the flow of signal fluid is fromthe pump to the directional control valves and to the work port channelsthereof via the signal conduit.

Valved Signal Means for Parallel Logic

Referring now to FIGS. 1, 8, and 13B, the valved signal means 188 ofFIG. 13B corresponds to valved signal means 128 of FIG. 1 except thatthe valved signal means 128 of FIG. 1 includes the attenuation flow path160 whereas the valved signal means 188 of FIG. 13B includes only thevalved signal means functions of communicating the signal passages 134aand 134b with the pressure inlet channel, as represented by the boxes198a and 198b, and with respective ones of the first work port channels86a and 86b. That is, when the valve spool 94 of the FIG. 1 embodimentis moved to the operating position of FIG. 8, the first signal passage134a is communicated to the first work port channel 86a; and the secondsignal passage 134b is communicated to the pressure inlet channel 92.

In like manner, if the movement of the valve spool 94 of FIGS. 1 and 8is considered to move rectangular boxes 194 of the FIG. 13B schematicillustration, then the same communications are made by valved signalmeans 188 of the FIG. 13B embodiment as are made by the valved signalmeans 128 of FIGS. 1 and 8 except for the elimination of the attenuationflow path 160 in the FIG. 13B embodiment. However, the fluid flowthrough a third fluid flow path 196 of the valved signal means 188 issimplified from that of the FIG. 1 embodiment since the third fluid flowpath 196 includes only fixed conductance restrictors 138b and 138awhereas the third fluid flow path 166 of FIG. 8 also includes therestrictor 146a of the one-way flow and reverse flow restrictor valves140a.

Referring now to FIGS. 13B-13D and 14B-14E, a letter X in a box, such asa box 195a of FIG. 13B, indicates that fluid communication is occluded;whereas the absence of any letter in such a box indicates the option ofoccluding fluid communication or establishing fluid communication with asump.

Referring now to FIG. 13C, the valved signal means 190 illustrates aportion of a directional control valve which is even more similar tothat of FIG. 1 than is the valved signal means 188 of FIG. 13B, in that,a third fluid flow path 166 of the valved signal means 190 includesone-way flow and reverse flow restrictor valves 202a and 202b whichsymbolically correspond to the one-way flow and reverse flow restrictorvalves 140a and 140b of FIG. 1 and which are inserted into respectiveones of signal passages 134a and 134b.

In like manner as the valved signal means 128 of FIGS. 1 and 8, thevalved signal means 190 includes valved or restricted flow path portions168 and 170 in the third fluid flow path 166. The valved signal means190 also includes valved or restricted flow path portions 169 and 171 ina fluid flow path 167 when the pressure inlet channel of the box 198a iscommunicated to the work port channel 86b via the signal passages 134aand 134b.

Referring now to FIG. 13D, the valved signal means 192 includes areverse fluid flow preventing means or one-way flow means whichcomprises a resiliently biased fluid restrictor or relief valve 204a anda reverse fluid flow restricting or preventing means which comprises acheck valve 206. The valved signal means 192 also includes signalpassages 208a and 208b having fixed conductance fluid restrictors 210aand 210b therein and check valves 212a and 212b.

In operation, the valved signal means 192 of FIG. 13D communicates apressure inlet channel, as symbolized by a box 214a, to a first workport channel 216a when the valve spool (not shown) of the directionalcontrol valve (not shown) thereof is in one operating position. In thisone operating position, pressurized fluid from the pressure inletchannel of the box 214a flows through the restrictor 210a and fromthence through the relief valve 204a to the first work port channel216a; so that a flow of signal fluid is furnished from the pressureinlet channel of the box 214a and is pressurized above the loadactuating pressure of the fluid pressure in the first work port channel216a by flow across the relief valve 204a.

This signal pressure, when increased above the load actuating pressurein the first work port channel 216a by the relief valve 204a is calledthe synthetic signal pressure. This synthetic signal pressure in aconduit 218a is supplied to the signal conduit 36 by way of the checkvalve 212a. At this same time, the signal passage 208b may becommunicated to a sump (not shown), or the signal passage 208b may beblocked from communication with any fluid passage. This alternatecommunication with a sump or this blocking of the second signal passage208b is symbolized in the valved signal means 192 by omission of anyletter or symbol in a box 220b.

When the control valve (not shown) having the valved signal means 192 ofFIG. 13D therein is actuated to another operating position, the secondsignal passage 208b is communicated to the pressure inlet channel, assymbolized by the box 214b, and a supply of signal fluid from thepressure inlet channel of the box 214b is delivered to a second workport channel 216b through the restrictor 210b, and then through both acheck valve 206 and a fixed conductance restrictor 222.

Thus the reverse flow preventing means or relief valve 204a functionsboth to prevent reverse flow and to add a predetermined pressuremagnitude to the fluid pressure in the conduit 218a over that in thefirst work port channel 216a; whereas both the reverse flow preventingmeans or check valve 206 and the fixed conductance restrictor 222 arerequired to prevent reverse flow and to add a predetermined pressuredifferential to the fluid flowing from a conduit 218b to the second workport channel 216b.

Referring again to FIG. 14E, it is well-known in the art that one-wayflow, or check valves, may or may not include springs, such as a spring205a of the reverse flow preventing means 204a. For purposes ofdescription herein, a relief valve includes a spring having a pressuredifferential effect on fluid flow that is substantially equal to orgreater than the fluid pressure effect of the spring 32 of the by-passvalve 26 of FIG. 3, or of the spring 54 of the pilot valve 52 of FIG.12.

In like manner, if the reverse flow preventing means 206 of FIG. 14Eimposes a fluid pressure differential, due to the flow rate of thesignal fluid therethrough that is substantially equal to or greater thanthe fluid pressure effect of either the spring 32 or the spring 54, thenthe valve 206 incorporates a restrictor function such as that of therestrictor 222; and the valve 206 may be used in place of, or incooperation with a separate restrictor such as the restrictor 222.

System with Series Logic

Referring now to FIGS. 14A-14E, series connected logic 228 includesthree-port logic valves 230a, 230b, 230c, and 230d and is used tointerconnect valved signal means 232, 234, 236, 238, and to select thehighest signal pressure from any of the valved signal means 232, 234,236, or 238. Series connected logic 228 functions the same as has beenfully described in U.S. Pat. No. 3,971,216 of common inventor entity andcommon assignee; so that the description which has been included in theaforementioned patent is included herein by reference and no detaileddescription is required herein. However, it is worthy of note that thethree-port logic valve 230c includes a first logic port 224c that isconnected to either the effective output operator 28 of FIG. 3 or to theeffective output operator 56 of FIG. 12 via the series-connectedthree-port logic valves 230a and 230b and via the signal conduit 36, asecond logic port 226c that is connected to the control port 130f ofFIG. 14D, and a third logic port 227c that is connected to thethree-port logic valve 230d to sense the fluid pressure in the controlport 130g.

Valved Signal Means for Series Logic

Referring now to FIG. 14B, the valved signal means 232 symbolizes thecommunications which a valved signal means would make in a four-positiondirectional control valve that includes a float position. As illustratedby fourth-position boxes 240a, 240b, and 240c, signal passages 242a and242b may be either blocked or communicated to a sump (not shown) asindicated by the absence of any symbol in the boxes 240a and 240b; and asignal or attenuation passage 244 is communicated to the second workport channel of the box 240c.

It is not important whether the attenuation passage 244 is communicatedto second work port channel of the box 240c, or blocked, or communicatedto a sump (not shown) except that one of the passages 242a, 242b, or 244must be communicated either to a sump or to a work port channel when thedirectional control valve of the valved signal means 232 is in the floatposition. Since in a four-position valve having a float position, bothwork port channels are communicated to respective ones of the returnchannels, communication of the attenuation passages 244 to the secondwork port channel of the box 240c is effective to attenuate any signalpressure in a conduit 218c and in a control port 130d.

Referring now to valved signal means 234 to FIG. 14C, the valved signalmeans 234 is the same as and functions the same as valved signal means192 of FIG. 13D except that: the valved signal means 234 includes tworeverse flow preventing means, 240a and 240b, of the relief valve typerather than using one reverse flow preventing means of the check valvetype such as the check valve 206 of the valved signal means 192, thevalved signal means 232 includes a three-port logic valve 250a forselecting the synthetic signal pressure from the conduits 218d and 218erather than using the check valves 212a and 212b of the valved signalmeans 192 of FIG. 13, the boxes 252a and 252b show the signal passage208a communicating to a sump for the stand-by position and one operatingposition, and the boxes 252d and 252c show the signal passage 208bcommunicating to a sump for the stand-by and another operating position.

The advantages of the valved signal means 192 of FIG. 13D and the valvedsignal means 234 of FIG. 14C is that the valved signal means, 192 or234, communicates directly with the work port channels 216a and 216bwithout being valved by the interaction of a valve spool and a valvebody; so that it is possible to interpose a flow control valve (shownand described in copending application of same inventor entity and samefiling date) between the valve spool and a work port of a directionalcontrol valve and to sense the load actuating pressure in one or both ofthe work port channels, 216a or 216b, without interference of thissensing function by the flow control device.

Valved signal means 236 of FIG. 14D is similar to the valved signalmeans 234 of FIG. 14C except that the furnishing of signal fluid fromthe pressure inlet channel of the box 214c to second work port channelof the box 199c by way of the signal passages 254b and 254c involves thevalving both of the signal passages 254b and 254c; whereas, in thevalved signal means 234 of FIG. 14C, the signal passage 208b is valvedto the conduit 218e but fluid flow in the conduit 218e is in constantfluid communication with the second work port channel 216b via therelief valve 204b.

Referring now to valved signal means 238 of FIG. 14E, the valved signalmeans 238 schematically illustrates the valved signal communicationsthat are made by the second preferred embodiment of the directionalcontrol valve as shown in FIGS. 15-18.

The valved signal means 238 of FIG. 14E includes a four-port connectedlogic valve 256, a control port 130g, signal passages 258a and 258b, andreverse flow preventing means or relief valve 204a and reverse flowpreventing means or check valve 206.

In a stand-by position as indicated by boxes 260a and 260b, the signalpassages 258a and 258b are both communicated to the return port means asindicated by the letter T in each of the boxes 260a and 260b; so thatthe control port 130g, a conduit 218h, and an unvalved logic port 271are all connected with a sump, as indicated by the letter T in the box260b, via a chamber 274 and the restrictor 210b to provide anattenuation flow path.

In a first operating position, as indicated by boxes 262a and 262b, bothof the signal passages, 258a and 258b, are communicated to a secondarysource of pressurized fluid as indicated by P₂ in the boxes 262a and262b. At this time, a third fluid flow path or restricted flow path 301,that includes a valved or restricted flow path portion 303 and arestricted flow path portion 305 communicates pump fluid from the P₂pressure inlet channel of the box 262a to the first work port channel216a via restrictor 210a and reverse flow preventing means 204a; and thefluid pressure in the conduit 218h is effective to actuate a ball orshuttle 268 away from a valved logic port 270a and into sealingengagement with a valved logic port 270b against the opposition of aspring 272.

Thus, the supplying of an additional flow of signal fluid, from the P₂pressure inlet channel of the box 262b, through the signal passage 258band the restrictor 210b into a chamber 274 of the four-port connectedlogic valve 256, is effective to add this flow of signal fluid from thechamber 274 to the conduit 218h and to the second work port channel 216avia the relief valve 204a since the ball or shuttle 268 is not blockingthe first valved logic port 270a.

In a second operating position as indicated by boxes 264a and 264b theconduit 218h is communicated to a return port means via the signalpassage 258a and the restrictor 210a therein so that any fluid pressurein the conduit 218h is attenuated by flow to a sump. Thus the spring 272is effective to seat the ball or shuttle 268 against the first valvedlogic port 270a. In the meantime the signal passage 258b is communicatedto the pressure inlet channel as indicated by box 264b; and fluid fromthe pressure inlet channel of the box 264b is communicated to the secondwork port channel 216b by way of the conduit 218j and the check valve206; so that a restricted flow path 307 is established that includesflow path portions 309 and 311.

Thus in both of the operating positions as described above, a supply ofsignal fluid flows to one of the work port channels, 216a or 216b, andthis flow of signal fluid is pressurized by flowing through either therelief valve 204a or the restrictor 222.

The unique feature of the valved signal means 238 is that, when thedirectional control valve (FIGS. 15-18) of the valved signal means 238is in a first operating position as indicated by boxes 262a and 262b,there are two separate flows of signal fluid being supplied to the firstwork port channel 216a from the pressure inlet channel. One of theseflows of signal fluid is through the restrictor 210a and the other isthrough the restrictor 210b. The reason for the two flows of signalfluid to the first work port channel 216a is one of convenience inarranging and optimizing the various fluid channels within thedirectional control valve and this optimization is made possible by thefour-port connection of the logic valve 256.

A Second Preferred Valve Embodiment

Referring now to FIGS. 15-18, directional control valve 280 includesvalve body 282 which is shown in phantom and movable valving element orvalve spool 284 which is slidably fitted into a spool bore 286.

In the FIG. 15 illustration the valve spool 284 is in the stand-byposition, in FIG. 16 the valve spool 284 has been moved to a firstoperating position, in FIG. 17 the valve spool 284 has been moved to asecond operating position, and in FIG. 18 the valve spool 284 has beenmoved to a float and regenerative position.

Referring now to FIG. 15, the spool bore 286 of the valve body 282 isintercepted by a return port means 288 that includes a regenerativechannel 290 and return channels 292a and 292b, first and second workport channels 294a and 294b, a pressure inlet channel 296, and anelongated circumferential groove 298 which serves as an interceptingmeans. The direction control valve 280 also includes a transfer orregenerative loop 300 which interconnects the second work port channel294b and the regenerative channel 290. A regenerative check valve 302 isinterposed into the transfer or regenerative loop 300 and is effectiveto prevent fluid flow from the second work port channel 294b to theregenerative channel 290. A low pressure relief valve 297 communicatesthe regenerative channel 290 to the first return channel 292a andthereby prevents applying excessive regenerative pressure to a point 304and to the second work port channel 294b. An orifice 306 communicatesthe regenerative channel 290 with the first return channel 292a toprovide an attenuation flow path, as will be subsequently described.

The second embodiment of FIGS. 15-18 includes a valved signal means 238which is identical to the valved signal means 238 of FIG. 14E. There arefour passages which communicate the valved signal means 238 with thespool bore 286 of the directional control valve 280. These four passagesare signal passages 308a and 308b which correspond to like numberedpassages for the valved signal means 238 of FIG. 14E, and signalpassages 258a and 258b which correspond to the like numbered signalpassages of the valved signal means 238 of FIG. 14E. Therefore, it isapparent that the schematic drawing of FIG. 14E symbolizes the operationof the portion of the directional control valve 280 of FIGS. 15-18 thatis called valved signal means 238.

Referring now to FIG. 17, the valve spool 284 includes land portions312a, 312b, 312c, 312d, and 312e; and the valve spool 284 also includesreduced cross-section portions 314a, 314b, 314c, and 314d. The landportion 312c includes a longitudinally extending groove 318, a radialbalancing hole 320, metering notches 322a and 322b, and metering notches324a and 324b. The valve spool 284 includes longitudinally disposed holemeans 328 which includes hole 330 and cross-holes 332 and 334. Conicalsections 336 and 337 are interposed between reduced cross-sectionportion 314a and respective ones of land portions 312a and 312b.Metering notches 338a and 338b intercept both the conical section 337and the land portion 312b.

Referring now to FIG. 18, tang and notch means 316 includes notches 340aand 340b, the metering notches 322a and 322b, and a longitudinallyextending tang 342a.

Referring now to FIG. 15, with the valve spool 284 in the stand-byposition as shown, the pressure inlet channel 296 is isolated from thework port channels 294a and 294b; and the work port channels 294a and294b are isolated from both the regenerative channel 290 and the returnchannels 292a and 292b.

Referring now to FIGS. 14E and 15, in the stand-by position, the signalpassage 258a is communicated to the first return channel 292a via holes334, 330, and 332, and the orifice 306 to provide an attenuation flowpath or fluid flow path 299, and to make the return port communicationwhich is illustrated by the box 260a of the valved signal means 238 ofFIG. 14E. Also, the signal passage 258b is communicated to the firstreturn channel 292a in a similar manner, seeing that the signal passage258b is only partially blocked by the tank 342a of the land portion312c. Thus the directional control valve 280 of the FIG. 15 embodimentmakes the valved signal means communications which are schematicallyillustrated by the boxes 260a and 260b of FIG. 14E; and fluid pressurein the control port 130g is attenuated by fluid flow to the returnchannel 292a via an attenuation flow path 299 which includes the logicvalve 256 and the signal passage 258b.

Referring now to FIG. 16, with the valve spool 284 moved to a firstoperating position as shown therein, a first fluid flow path 344, whichincludes flow path portions 346a and 346b has been established from thepressure inlet channel 296 to the first work port channel 294a; and asecond fluid flow path 348 has been established from the second workport channel 294b to the second return channel 292b.

At this time, the attenuation flow path 299 of FIG. 15 which has beencommunicating the signal passage 258a with the regenerative channel 290and with the first return channel 292a via the orifice 306, has now beenoccluded by movement of the cross-hole 332 to a position that is remotefrom the regenerative channel 290; and the signal passage 258b has beencommunicated with a bore portion 350 of the spool bore 286.

The valve spool 284 is timed with respect to the pressure inlet channel296, the circumferential groove or intercepting means 298, and the workport channel 294a so that the fluid pressure in the bore portion 350approximates the fluid pressure in the pressure inlet channel 296. Thefluid pressure in the signal passage 258b is the P₂ pressure of theelongated groove 298 of FIG. 16 as indicated by the box 262b in FIG.14E. Also, the same or nearly the same fluid pressure is applied to thesignal passage 258a from the elongated groove 298 of FIG. 16, and thisis represented by P₂ in the box 262a in FIG. 14E.

Therefore, not only is the third fluid flow path 301 established withportions 303 and 305 thereof, but also a flow path portion 319 isestablished from the signal passage 258b to the chamber 274 of the logicvalve 256. The fluid pressure from the signal passage 258a is effectiveto actuate the ball 268 to the right against the force of the spring 272and into sealing engagement with the valved logic port 270b, and to openthe valved logic port 270a; so that pressurized fluid from both the flowpath portion 303 and the flow path portion 319 flows to the work portchannel 294a via the flow path portion 305.

Referring finally to FIG. 16, and the land portion 312b has a shorterlength than does the groove 298. The first fluid flow path 344 isestablished by positioning the land portion 312b within the confines ofthe groove 298; and the first fluid flow path 344 includes the reducedcross-section portion 314b, the bore portion 350, the groove 298,another bore portion 351, and the reduced cross-section portion 314a.

Referring now to FIG. 17, the valve spool 284 has been moved to a secondoperating position wherein another first fluid flow path 352 has beenestablished from the pressure inlet channel 296 to the second work portchannel 294b; and another second fluid flow path 354 has beenestablished from the first work port channel 294a to the regenerativechannel 290 of the return port means 288. At this time, the first signalpassage 258a is communicated to the first return channel 292a via thelongitudinally disposed hole means 328 and the orifice 306; and thesecond signal passage 258b is communicated to the pressure inlet channel296 via the longitudinally extending groove 318 of the land portion312c. Thus the communications of the signal passages 258a and 258b areas illustrated by the boxes 264a and 264b of FIG. 14E; and therestricted flow path 307 with the portions 309 and 311 thereof areestablished as previously described for FIG. 14E.

Referring now to FIG. 18, the valve spool 284 has been moved to a floatand regenerative position in which the first work port channel 294a iscommunicated to the first return channel 292a by the reducedcross-section portion 314a; and the second work port channel 294b iscommunicated to the second return channel 292b by the reducedcross-section portion 314d.

At this time, the first signal passage 258a is communicated to the firstreturn channel 292a by the longitudinally disposed hole means 328; andthe second signal passage 258b is communicated to the first returnchannel 292a by the longitudinally extending groove 318 and thelongitudinally disposed hole means 328.

Therefore the valve embodiment of FIGS. 15-18 provides the functions ofthe valved signal means 238 of FIG. 14E as indicated by the boxes 262aand 262b, 260a and 260b, 264a and 264b, and 310a and 310b.

The directional control valve embodiment of FIGS. 15-18 is similar tothe directional control valve of common inventor entity, commonassignee, and common filing date which includes a flow control valvethat is interposed between the valve spool 284 and the first work portchannel 294a of the present invention; and the detailed description ofthe directional control valve of the referenced application of commonfiling date is included herein by reference thereto.

Second Embodiment with Flow Control

Referring now to FIG. 19, a directional control valve 360 is similar tothe directional control valve 280 of FIGS. 15-18. The directionalcontrol valve 360 differs primarily in that a flow control means 362 isincluded in a body 364 of the directional control valve 360.

The flow control means 362 includes a plunger 366 that is slidablyfitted into a plunger bore 368, that is spring centered by springs 370aand 370b, and that includes a reduced cross-section portion 372intermediate of land portions 374 and 376.

A work port channel 378 and a service channel 380 intercept the plungerbore 368; and the service channel 380 intercepts the spool bore 286. Aconduit 382 interconnects the service channel 380 and a chamber 384 forfluid pressure actuation of the plunger 366 in one direction; and aconduit 386 interconnects the circumferential groove 298 and a chamber388 for fluid pressure actuation of the plunger 366 in the otherdirection.

The valved signal means 238 includes the same component parts andestablishes the same fluid flow paths and has been described for FIGS.15-18; but in FIG. 19, the work port channel 378 does not intercept thespool bore 286, so that the conduit 218h and the passage 308a have beenlengthened and the relief valve 204a has been relocated.

The operation of the flow control means may be understood by referenceto FIG. 19 along with FIGS. 15, 17 and 18 by those familiar to the art,or by reference to the detailed description, which is incorporatedherein by reference thereto, of the copending patent application ofcommon inventorship entity, common assignee, and common filing date.

Briefly, the valve spool 284 is movable to a first operating positionwherein a flow path portion 346b is established and selectively sized,wherein fluid pressure upstream of the flow path portion 346b issupplied to the chamber 388 via the circumferential groove 298 and theconduit 386, and wherein the fluid pressure in the service channel 380is supplied to the chamber 384 via the conduit 382. The plunger 366 isactuated by these two fluid pressures to maintain a rate of fluid flowthat results in a substantially constant differential pressure betweenthe groove 298 and the service channel 380 for fluid flow to the workport channel 378.

When the valve spool 284 is moved to the second operating position ofFIG. 17, the chamber 388 is communicated to the regenerative channel 290by the longitudinal hole means 328; so that the plunger 366 is actuatedby fluid pressures in the service channel 380 and in the regenerativechannel 290 to maintain a substantially constant pressure differentialtherebetween; whereby the rate of fluid flow from the work port channel378 to the regenerative channel 290 is maintained substantiallyproportional to the sizing of the fluid flow path 354 of FIG. 17.

First Embodiment Details and Modifications

Referring now to FIGS. 1 and 1A, the signal passage 134a includes afirst hole portion 131a and a second hole portion 133a that orthogonallyintercept diametrically opposite sides of a cylindrical bore surface 129of the spool bore 84; and, in like manner, the second signal passage134b includes a first hole portion 131b and a second hole portion 133b.

The tangs 110a and 110b must be longitudinally and rotationallypositioned to sealingly engage the cylindrical bore surface 129 wherethe first hole portions 131a and 131b intercept the spool bore 84 whenthe valve spool 94 is in the stand-by position. Second hole portions133a and 133b are provided for the purpose of balancing radial pressureforces on the valve spool; and radial pressure balancing means, such asthe radial balancing holes 112a and 112b of FIG. 1, or radial pressurebalancing hole portions 113a, 113b, 115a, and 115b, must be provided toequalize the fluid pressures in respective hole portions of the signalpassages 134a and 134b.

While it is desirable that the radial balancing holes 112a and 112bintercept both of the cylindrical surface portions, such as thecylindrical surface portions 150a and 150b of FIG. 7, at the samelongitudinal position, it is not necessary that the balancing holeportions, such as the hole portions 115a and 115b, orthogonallyintercept the cylindrical surface portions, such as the cylindricalsurface portions 150a and 150b. Since machining ease, machining cycletime, and positional accuracy are enhanced by drilling fromdiametrically opposite sides of the valve spool 94, it is practical tolongitudinally incline the balancing hole portions 113a, 113b, 115a, and115b as desired as long as there is a hole means, such as the holeportions 115a and 115b that intercept the surface portions 150a and 150band that intercommunicate the hole portions 131b and 133b.

The longitudinally extending grooves 106a and 106b of FIG. 1 providepassage means in the valve spool 94 for the establishing of the flowpath portion 169; and the cross-sectional area of the groove can besized to provide a fluid restriction in the flow path portion 169.Alternately an elongated circumferential groove 139, as shown in FIG. 1Amay be used as a passage means in a valve spool 141; and the diameter ofthe circumferential groove 139 may be sized to limit the conductance ofthe flow path portion 169.

Even if the circumferential groove 139 is not sufficiently long tocommunicate the pressure inlet channel 92 to the signal passage 134a toestablish the flow path portion 169 and thereby to serve as a passagemeans in the valve spool 141, it will still function as a radialbalancing means when the valve spool is moved to a longitudinal positionwherein the circumferential groove 139 intercommunicates the holeportions 131a and 133a.

SUMMARIZING COMMENTS

Both the first embodiment of the directional control valve of thepresent invention as shown in FIGS. 1, 2, 6, and 8, and the secondembodiment as shown in FIGS. 15-18, supply a flow of signal fluid totheir respective work port channels and pressurize these signal fluidsto respective synthetic signal pressures which are at a predeterminedpressure magnitude above the load actuating pressures in the respectivework port channels.

The portion of each directional control valve that controls thesupplying of signal fluid to a respective one of the work port channels,and that pressurizes the signal fluid to synthetic signal pressures, iscalled the valved signal means and is typified by the valved signalmeans 128 of FIGS. 1, 2, 8, and 9, and the valved signal means 238 ofFIGS. 15-18.

Valved signal means 238 is also shown in schematic form in FIG. 14E; andthe similarities and differences of both the valved signal means 188 ofFIG. 13B and the valved signal means 190 of FIG. 13C to the embodimentof FIGS. 1, 2, 8, and 9 have been discussed. Also, the functioning ofvalved signal means 192, 232, 234, and 236 of FIGS. 13D and 14B-14D havebeen described sufficiently that anyone skilled in the art could designa directional control valve embodying one of the valved signal meansdescribed herein or a variation thereof.

Each valved signal means establishes and occludes a fluid flow path orrestricted flow path, such as the fluid flow path 166 of FIG. 8 or 301of FIG. 16, or 307 of FIG. 17, from a source of pressurized fluid, suchas the pressure inlet channel 92 of FIG. 8, to a work port channel, suchas the work port channel 86a of FIG. 8.

Each restricted flow path, such as 166, 301, or 307, includes one flowpath portion, such as 168, 303, or 309, that communicates a pressureinlet channel, 92 or 296, with a control port, 130 or 130g, and thatincludes a first fluid restrictor therein.

The first fluid restrictor may be the grooves 106a and 106b and/orrestrictor 138a or 138b of FIG. 8, or 210a of FIG. 16, or 318 and/or210b of FIG. 17.

Each restricted flow path also includes another flow path portion suchas the flow path portion 170 of FIG. 8, 305 of FIG. 16, or 311 of FIG.17, that communicates the control port, 130 or 130g, to a work portchannel, 86a, 86b, 294a, or 294b.

These other flow path portions may be valved flow path portions, such asthe flow path portion 170, or they may be one-way flow path portions,such as the flow path portions 305 and 311.

Each valved signal means includes reverse flow preventing means toprevent fluid from flowing from a work port channel, such as 86a, 216a,or 216b, to a control port, such as 130 or 130g, when the valve spool isin the stand-by position. This reverse flow preventing means may be aportion of a valve spool such as the tang 110a of the valve spool 94 ofFIGS. 1 and 2, or the reverse flow preventing means may be a one-wayflow and reverse flow restrictor valve such as the relief valve 204a orthe check valve 206 of FIG. 15.

That is, a valved flow path portion, such as flow path portion 170utilizes a portion of the valve spool, such as the tang 110a as areverse flow preventing means; and a one-way flow path portion uses arelief valve, such as the relief valve 204a of FIG. 16, or a checkvalve, such as the check valve 206 of FIG. 17, as a reverse flowpreventing means.

Preferably, each of these other flow path portions, 170, 305, and 311,includes second fluid restrictor means therein. This second fluidrestrictor means may be the fixed conductance restriction of therestrictor or groove 146a of the one-way flow and restrictor valve 140aof FIG. 8, the fixed conductance restriction of the restrictor 138a ofFIG. 8, the resiliently biased restrictor or relief valve 204a of FIG.16 in which the resilient bias is provided by the spring 205a, the fixedconductance restrictor 222 of FIG. 17, the fixed conductance of thecheck valve 206 of FIG. 17, or both the resilient bias of the spring205a and the fixed conductance through the relief valve 204a of FIG. 16.

That is, anything in a restricted flow path, such as the flow path 301of FIG. 16, that increases the fluid pressure in a control port, 130 or130g, above the load actuating pressure in a work port channel, 294a, bya pressure magnitude that is substantially equal to or greater than thestand-by pressure of the system as determined by the spring 32 of FIG.3, or the spring 54 of FIG. 12, or that increases the signal pressuresubstantially equal to or more than 50 psi, is a second fluid restrictormeans as defined herein.

Both of the embodiments of directional control valves, FIGS. 1, 2, 8,and 9, and FIGS. 15-18, are usable with both fixed displacement andvariable displacement pumps as typified by FIGS. 3 and 12.

Both of the embodiments of directional control valves are usable witheither the series-connected logic of FIG. 14A, or the parallel-connectedlogic in FIG. 14.

The valved signal means of FIGS. 14B-14E are usable with either thelogic of FIG. 14A or the logic of FIG. 13A; but the valved signal meansof FIGS. 13B-13D are only usable with the logic of FIG. 13A.

The three-port logic valve 230d of FIG. 14A is redundant as is the sump24g; and the valved logic port 227c can be connected to the control port130g without any change in functioning, as can be seen by inspection.

While there have been described above the principles of this inventionin connection with specific apparatus, it is to be clearly understoodthat this description is made only by way of example and not as alimitation to the scope of the claims.

What is claimed is:
 1. A load responsive hydraulic system (FIG. 3 orFIG. 12,+FIG. 1 or FIG. 15) which comprises a source (20 of FIG. 3, or46 of FIG. 12) of pressurized fluid having a pump (22 or 48) and a sump(24a or 24b);effective output means (26 or 60), being connected to saidsource and having an effective output operator (28 or 56), forcontrolling the effective output of said pump in response to fluidpressure applied to said effective output operator; a fluid actuateddevice (156 of FIG. 1) having first (158a) and second (158b) actuatingports; a directional control valve (80 of FIG. 1, or 280 of FIG. 15)having a pressure inlet channel (92 or 296) that is connected to saidpump, having return port means (88 or 288) for return of excess fluid tosaid source, having a first work port channel (86a or 294a) that isconnected to said first actuating port and a second work port channel(86b or 294b) that is connected to said second actuating port, andhaving movable valving element means (94 or 284) that is movable from astand-by position (FIG. 1 or FIG. 15) to an operating position (FIG. 8or FIG. 16), for establishing both a first fluid flow path (162 of FIG.9, or 344 of FIG. 16) from said pressure inlet channel to said firstwork port channel and a second fluid flow path (164 of FIG. 9, or 348 ofFIG. 16) from said second work port channel to said return port means assaid valving element means is moved to said operating position, and foroccluding both said first and second fluid flow paths when said valvingelement means is moved to said stand-by position; valved signal means(128 or 238), including a control port (130 or 130g), for establishing arestricted flow path (166 of FIG. 8, or 301 of FIG. 16) from said pumpto said first work port channel after said second fluid flow path isestablished, for providing a fluid restriction (106a or 138b of FIG. 8,or 258a of FIG. 16) in said restricted flow path, for sensing fluidpressure in said third fluid flow path intermediate of said fluidrestriction and said first work port channel, for applying said sensedfluid pressure to said control port, and for occluding said restrictedflow path before said occlusion of said second fluid flow path; andmeans (36, 230a, etc.) for applying said sensed fluid pressure to saideffective output operator.
 2. A load responsive hydraulic system asclaimed in claim 1 in which said system includes means for attenuating(160 of FIG. 1, 299 of FIG. 15, or 185 of FIG. 13A) said sensed fluidpressure when said valving element means (94 or 284) is in said stand-byposition (FIG. 1 or FIG. 15).
 3. A load responsive hydraulic system asclaimed in claim 2 in which said attenuating means comprises anattenuation flow path (160 or 299) that is established from said controlport (130 or 130g) to said sump by said directional control valve (80 or280) when valving element means is in said stand-by position (FIG. 1 orFIG. 15).
 4. A load responsive hydraulic system as claimed in claim 2 inwhich said attenuating means comprises a fluid restrictor (185 of FIG.13A) that communicates said effective output operator (28 of FIG. 3 or56 of FIG. 12) to said sump.
 5. A load responsive hydraulic system asclaimed in claim 1 in which said valved signal means (128 of FIG. 1, or238 of FIG. 15) includes second fluid restriction means (138a or 146a ofFIG. 1, or 204a or 222 of FIG. 15) for providing a predeterminedresistance of fluid flow from said control port (130 or 130g) to saidfirst work port channel (86a or 294a).
 6. A load responsive hydraulicsystem (FIG. 3 or FIG. 12,+FIG. 1 or FIG. 15) which comprises a source(20 or 46) of presurized fluid having a pump (22 or 48) and a sump (24aor 24b);effective output means (26 or 60), being connected to saidsource and having an effective output operator (28 or 56), forcontrolling the effective output of said pump in response to fluidpressure applied to said effective output operator; a fluid actuateddevice (156) having first (158a) and second (158b) actuating ports; adirectional control valve (80 or 280) having a pressure inlet channel(92 or 296) that is connected to said pump, having return port means (88or 288) for return of excess fluid to said source, having a first workport channel (86a or 294a ) that is connected to said first actuatingport and a second work port channel (86b or 294b) that is connected tosaid second actuating port, and having movable valving element means (94or 284) that is movable from a stand-by position (FIG. 1, or FIG. 15) toan operating position (FIG. 8, or FIG. 16, or FIG. 17), for establishingboth a first fluid flow path (162 of FIG. 9, 163 of FIG. 1, 344 of FIG.16, or 352 of FIG. 17) from said pressure inlet channel to said firstwork port channel and a second fluid flow path (348) from said secondwork port channel to said return port means as said valving elementmeans is moved to said operating position, and for occluding both saidfirst and second fluid flow paths when said valving element means ismoved to said stand-by position; valved signal means (128 or 238),including a control port (130 or 130g), for establishing a restrictedflow path (166 or FIG. 8, 167 of FIG. 1, 301 of FIG. 16, or 307 of FIG.17) from said pump to said first work port channel after said secondfluid flow path is established, for providing a fluid restriction (106aor 138b of FIG. 8, 210a of FIG. 16, or 210b or 318 of FIG. 17) in saidrestricted flow path, for sensing fluid pressure in said restricted flowpath intermediate of said fluid restriction and said first work portchannel, for applying said sensed fluid pressure to said control port,and for occluding said restricted flow path before said occlusion ofsaid second fluid flow path; and logic means (182a+182b of FIG. 13A, or230a+230b of FIG. 14A), having a first logic port (183 of FIG. 13A, or224c of FIG. 14A) that is connected to said effective output operator,having a second logic port (179a of FIG. 13A, or 226c of FIG. 14A) thatis connected to said control port, and having a third logic port (179bof FIG. 13A, or 227c of FIG. 14A) that is adapted for connection to afluid pressure, for establishing fluid communication to said first logicport and to said effective output operator from the one of the other twoof said logic ports having the higher fluid pressure therein, and forpreventing fluid flow from said first logic port to the one of said twoother logic ports with the lower fluid pressure therein.
 7. A loadresponsive hydraulic system as claimed in claim 6 in which said logicmeans comprises a three-port logic valve (230c of FIG. 14A).
 8. A loadresponsive hydraulic system as claimed in claim 6 in which said logicmeans comprises a first one-way flow valve (182a) communicating saidcontrol port (130 or 130g) to said effective output operator (28 or 56)and preventing reverse flow therebetween, and a second one-way flowvalve (182b) communicating said third logic port (179b) to saideffective output operator and preventing reverse flow therebetween.
 9. Aload responsive hydraulic system as claimed in claim 8 in which saidsystem includes means for attenuating (160 of FIG. 1, 299 of FIG. 15, or185 of FIG. 13A) said higher fluid pressure applied to said effectiveoutput operator when said valving element means is in said stand-byposition (FIG. 1, or FIG. 15).
 10. A load responsive hydraulic system asclaimed in claim 9 in which said attenuating means comprises a fourthfluid flow path (160 of FIG. 1, or 299 of FIG. 15) that is establishedfrom said control port (130 or 130g) to said sump by said directionalcontrol valve (80 or 280) when said valving element means (94 or 284) isin said stand-by position (FIG. 1 or FIG. 15).
 11. A load responsivehydraulic system as claimed in claim 9 in which said attenuating meanscomprises a restrictor (185 of FIG. 13A) that communicates saideffective output operator (28 of FIG 3, or 56 of FIG. 12) to said sump(24f of FIG. 13A).
 12. A load responsive hydraulic system as claimed inclaim 8 in which said valved signal means (128 or 238) includes secondfluid restrictor means (138a or 146a of FIG. 8, or 204a of FIG. 16, or222 of FIG. 17) for providing predetermined resistance to fluid flowfrom said control port (130 or 130g) to said first work port channel(86a, 294a, or 294b).
 13. A load responsive hydraulic system (FIG. 3 orFIG. 12,+FIG. 1 or FIG. 15) of the type having a source (20 or 46) ofpressurized fluid that includes a pump (22 or 48) and a sump (24a or24b), having effective output means (26 or 60) that includes aneffective output operator (28 or 56) for control of the pressure andeffective output of said pump in response to a signal pressure appliedto said effective output operator, having a fluid actuated device (156)that includes first (158a) and second (158b) actuating ports, and havinga directional control valve (80 or 280) that is operatively connected tosaid source and to said actuating ports and that includes movablevalving element means (94 or 284) for establishing a first fluid flowpath (162, or 344=346a+346b) from said pump to said first actuating portat the load actuating pressure of said device and for establishing asecond fluid flow path (164 or 348) from said second actuating port tosaid sump when said valving element means is moved to an operatingposition, an for occluding said first and second fluid flow paths whensaid valving element means is moved to a stand-by position, theimprovement which comprises:valved signal means (128 or 238), comprisinga control port (130 or 130g), comprising first (134a or 258a) and second(134b or 308a) signal passages in said directional control valve thatcommunicate with said movable valving element means, and comprisingcooperating portions (106a+102+110a, or 314b+312c) of said valvingelement means, for supplying signal fluid from said pump to said firstactuating port after said second fluid flow path is established, forpressurizing said signal fluid into a predetermined pressurerelationship to said load actuating pressure, and for occluding saidsupply of signal fluid before said occluding of said second fluid flowpath; and means (36), being operatively connected to said valved signalmeans and to said effective output operator, for applying saidpressurized signal fluid to said effective output operator.
 14. A loadresponsive hydraulic system as claimed in claim 13 in which saidpredetermined pressure relationship comprises pressurizing said signalfluid to a predetermined pressure magnitude above said load actuatingpressure.
 15. A load responsive hydraulic system (FIG. 3 or FIG.12,+FIG. 1 or FIG. 15) of the type having a source (20 or 46) ofpressurized fluid that includes a pump (22 or 48) and a sump (24a or24b), having effective output means (26 or 60) that includes aneffective output operator (28 or 56) for control of the pressure andeffective output of said pump in response to a signal pressure appliedto said effective output operator, having a fluid actuated device (156)that includes first (158a) and second (158b) actuating ports, and havinga directional control valve (80 or 280) that includes a pressure inletchannel (92 or 296) connected to said source, that includes first (86aor 294a) and second (86b or 294b) work port channels operativelyconnected to respective ones of said actuating ports, that includesreturn port means (88 or 288) operatively connected to said sump, andthat includes movable valving element means (94 or 284) for establishingboth a first fluid flow path (162, or 344=346a+346b) from said pump tosaid first actuating port at the load actuating pressure of said deviceand a second fluid flow path (164 or 348) from said second actuatingport to said return port means when said valving element means is movedto an operating position, and for occluding said first and second fluidflow paths when said valving element means is moved to a stand-byposition, the improvement which comprises:valved signal means (128 or238), comprising a control port (130 or 130g), comprising first (134a or258a) and second (134b or 308a) signal passages in said directionalcontrol valve that communicate with said movable valving element means,and comprising cooperating portions (106a+102+110a, or 318+314b+312c) ofsaid valving element means, for establishing a third fluid flow path(166 of FIG. 8, or 301 of FIG. 16) from said pressure inlet channel tosaid first work port channel after said second fluid flow path isestablished, for providing a fluid restriction (106a or 138b of FIG. 8,or 258a of FIG. 16) in said third fluid flow path, for sensing fluidpressure in said third fluid flow path intermediate of said fluidrestriction and said first work port channel, for applying said sensedfluid pressure to said control port, and for occluding said restrictedflow path before said occlusion of said second fluid flow path; andmeans (36, 230a, etc.), being operatively connected to said control portand to said effective output operator, for applying said sensed fluidpressure to said effective output operator.
 16. A load responsivehydraulic system (FIG. 3 or FIG. 12,+FIG. 1 or FIG. 15) as claimed inclaim 15 in which said control valve includes second fluid restrictionmeans (138a or 146a of FIG. 8, or 204a or 222 of FIGS. 14E & 15), beinginserted into said third fluid flow path (166 of FIG. 8, 301 of FIGS.14E & 15, or 307 of FIGS. 14E & 15) intermediate of said first work portchannel (86a, 294a, or 294b) and said communicating of said third fluidflow path to said control port (130 or 130g), for providing apredetermined resistance to fluid flow from first said fluid restriction(138b, 210a, or 210b) to said first work port channel (86a, 294a, or294b).
 17. A load responsive hydraulic system (FIG. 3 or FIG. 12,+FIG. 1or FIG. 15) as claimed in claim 16 in which said second fluid restrictormeans comprises a fixed conductance restrictor (138a or 146a of FIG. 8,or 222 of FIGS. 14E and 15).
 18. A load responsive hydraulic system (FIG. 3 or FIG. 12,+FIG. 15) as claimed in claim 16 in which said secondfluid restrictor means comprises a resiliently biased fluid restrictor(204a of FIGS. 14E and 15).
 19. A load responsive hydraulic system (FIG.3 or FIG. 12,+FIG. 1 or FIG. 15) as claimed in claim 15 in which saidthird fluid flow path of said valved signal means (128 of FIG. 8, or 238of FIGS. 14E & 15) comprises series-connected first (168 of FIG. 8, or303 of FIGS. 14E & 16, or 309 of FIGS. 14E & 17) and second (170 of FIG.8, or 305 of FIGS. 14E & 16, or 311 of FIGS. 14E & 17) flow pathportions with said first flow path portion communicating with saidpressure inlet channel (92 or 296), with said second flow path portioncommunicating with said first work port channel (86a, 294a, or 294b),with said fluid restriction (138b of FIG. 8, or 210a or 210b of FIGS.14E & 15) thereof being disposed in said first flow path portion, withsaid communicating to said control port (130 or 130g) being from saidseries connection (132 of FIG. 8, or 218h or 218j of FIGS. 14E & 15) ofsaid first and second flow path portions, and with said establishing andoccluding of said third fluid flow path comprising establishing andoccluding one (168 or 170 of FIG. 8, or 303 of FIGS. 14E & 16, or 309 ofFIGS. 14E & 17) of said flow path portions; andmeans (110a of FIG. 2, or204a or 206 of FIGS. 14E & 15) for preventing reverse fluid flow fromsaid first work port channel (86a of FIG. 8, or 216a or 216b of FIGS.14E & 15) to said control port via said second flow path portion whensaid movable valving element means (94 or 284) is in said stand-byposition (FIG. 1 or FIG. 15).
 20. A load responsive hydraulic system(FIG. 3 or FIG. 12,+FIG. 1) as claimed in claim 19 in which said meansfor preventing reverse fluid flow comprises occluding (by 110a of FIG.2) said second flow path portion (170 of FIG. 8) when said movablevalving element means (94) is in said stand-by position (FIG. 1).
 21. Aload responsive hydraulic system (FIG. 3 or FIG. 12+FIG. 1) as claimedin claim 20 in which said second fluid flow path (164 of FIG. 9) isestablished before said second flow path portion (170 of FIG. 8) of saidthird fluid flow path (166 of FIG. 8) is established and said secondflow path portion (170 of FIG. 8) is established before said first flowpath portion (168 of FIG. 8) is established (via 106a of FIG. 8) as saidvalving element means (94) is moved to said operating position (FIGS. 8and 9); andsaid first flow path portion (168 of FIG. 8) is occludedbefore said second flow path portion (170 of FIG. 8) is occluded andsaid second flow path portion (170 of FIG. 8) is occluded before saidsecond fluid flow path (164 of FIG. 9) is occluded as said valvingelement means is moved to said stand-by position (FIGS. 1 and 2).
 22. Aload responsive hydraulic system (FIG. 3 or FIG. 12,+FIG. 15) as claimedin claim 19 in which said means for preventing reverse flow comprisesone-way flow means (204a or 206 of FIGS. 14E & 15), being interposedinto said second flow path portion (305 of FIGS. 14E & 16, or 311 ofFIGS. 14E & 17), for restricting fluid communication from said firstwork port channel (216a or 216b of FIGS. 14E & 15) to said control port(130g).
 23. A load responsive hydraulic system (FIG. 3 or FIG. 12,+FIG.15) as claimed in claim 22 in which said one-way flow means comprises acheck valve (206 of FIGS. 14E & 15).
 24. A load responsive hydraulicsystem (FIG. 3 or FIG. 12,+FIG. 15) as claimed in claim 22 in which saidone-way flow means comprises a resiliently biased fluid restrictor (204aof FIGS. 14E and 15).
 25. A load responsive hydraulic system (FIG. 3 orFIG. 12,+FIG. 1 or FIG. 15) as claimed in claim 15 in which said movablevalving element means (94 of FIG. 1, or 284 of FIG. 15) includescooperating portions (98+126+148 of FIG. 1, or 330+332+334 of FIG. 15)thereof for establishing a fourth fluid flow path (160 of FIG. 1, or 299of FIG. 15) from said control port (130 of FIG. 1, or 130g of FIG. 15)to said return port means (88 of FIG. 2, or 288 of FIG. 15) when saidvalving element means is in said stand-by position (FIGS. 1 and 2, orFIG. 15) and for occluding said fourth fluid flow path when said thirdfluid flow path (166 of FIG. 8, or 301 of FIG. 16, or 307 of FIG. 17) isestablished.
 26. A load responsive hydraulic system (FIG. 3 or FIG.12,+FIG. 1 or FIG. 15) as claimed in claim 25 in which said fourth fluidflow path (160 of FIG. 1, or 299 of FIG. 15) is occluded before saidthird fluid flow path (166 of FIG. 8, or 301 of FIG. 16, or 307 of FIG.17) is established as said valving element means is moved from saidstand-by position (FIGS. 1 and 2, or FIG. 15) to said operating position(FIGS. 8 and 9, or FIG. 16, or FIG. 17); andsaid fourth fluid flow pathis established after said third fluid flow path is occluded as saidvalving element means is moved from said operating position to saidstand-by position.
 27. A load responsive hydraulic system (FIG. 3 orFIG. 12,+FIG. 1) as claimed in claim 15 in which said directionalcontrol valve (80) comprises a valve body (82) having a spool bore (84)therein;said movable valving element means comprises a valve spool (94)being slidably inserted into said spool bore and having a land portion(100); and said valved signal means (128) comprises a pair oflongitudinally extending grooves (106a & 106b) in said land portion. 28.A load responsive hydraulic system (FIG. 3 or FIG. 12,+FIG. 1) asclaimed in claim 15 in which said directional control valve (80)comprises a valve body (82) having a spool bore (84) therein;saidmovable valving element means comprises a valve spool (94) beingslidably inserted into said spool bore and having a land portion (100);and said valved signal means (128) both comprises a longitudinallyextending tang 110a that is formed on one end of said land portion by apair of diametrically opposite tang notches (118a & 118b), and radialpressure balancing means, comprising a hole (112a) that is transverselydisposed in said valve spool, for providing radial pressure balancing tosaid longitudinally extending tang.
 29. A load responsive hydraulicsystem (FIG. 3 or FIG. 12,+FIG. 1) as claimed in claim 15 in which saiddirectional control valve (80) comprises a valve body (82) having aspool bore (84) therein;said return port means (88) comprises first(90a) and second (90b) return port channels that intercept said spoolbore at spaced-apart locations; said work port channels (90a & 90b)intercept said spool bore at spaced-apart locations intermediate of saidreturn port channels; said pressure inlet channel (92) intercepts saidspool bore intermediate of said work port channels; and saidcommunicating of said signal passages (134a & 134b) with said movablevalving element means (94) comprises said signal passages interceptingsaid spool bore intermediate of said pressure inlet channel andrespective ones of said work port channels.
 30. A load responsivehydraulic system (FIG. 3 or FIG. 12,+FIG. 15) as claimed in claim 15 inwhich said directional control valve (280) comprises a valve body (282)having a spool bore (286) therein;said return port means (288) comprisestwo (292a & 292b) return port channels that intercept said spool bore inspaced-apart locations; said work port channels (294a & 294b) interceptsaid spool bore in spaced-apart locations intermediate of said returnport channels; said pressure inlet channel (296) intercepts said spoolbore intermediate of said work port channels; said communicating of one(308a or 308b) of said signal passages with said movable valving elementmeans (284) comprises said one signal passage (308a or 308b)intercepting one (294a or 294b) of said work port channels; and saidcommunicating of the other (258a or 258b) of said signal passages withsaid movable valving element means (284) comprises said other (258a or258b) signal passage intercepting said spool bore intermediate of saidpressure inlet channel and one of said work port channels.
 31. A loadresponsive hydraulic system (FIG. 3 or FIG. 12,+FIG. 1 or FIG. 15) ofthe type having a source (20 or 46) of pressurized fluid that includes apump (22 or 48) and a sump (24a or 24b), having effective output means(26 or 60) that includes an effective output operator (28 or 56) forcontrol of the pressure and effective output of said pump in response toa signal pressure applied to said effective output operator, having afluid actuated device (156) that includes first (158a) and second (158b)actuating ports, and having a directional control valve (80 or 280) thatincludes a pressure inlet channel (92 or 296) connected to said source,that includes first (86a or 294a) and second (86b or 294b) work portchannels operatively connected to respective ones of said actuatingports, that includes return port means (88 or 288) operatively connectedto said sump, and that includes movable valving element means (94 or284) for establishing both a first fluid flow path (162, or344=346a+346b) from said pump to said first actuating port at the loadactuating pressure of said device and a second fluid flow path (164 or348) from said second actuating port to said return port means when saidvalving element means is moved to an operating position, and foroccluding said first and second fluid flow paths when said valvingelement means is moved to a stand-by position, the improvement whichcomprises:valved signal means (128 or 238), comprising a control port(130 or 130g), comprising first (134a or 254a) and second (134b or 308a)signal passages in said directional control valve that communicates withsaid movable valving element means, and comprising cooperating portions(106a+102+110a, or 318+314b+312c) of said valving element means, forestablishing a third fluid flow path (166 of FIG. 8, 167 of FIG. 1, 301of FIG. 16, or 307 of FIG. 17) from said pump to said first work portchannel after said second fluid flow path is established, for providinga fluid restriction (106a or 138b of FIG. 8, 210a of FIG. 16, or 210b or318 of FIG. 17) in said third fluid flow path, for sensing fluidpressure in said third fluid flow path intermediate of said fluidrestriction and said first work port channel, for applying said sensedfluid pressure to said control port, and for occluding said restrictedflow path before said occlusion of said second fluid flow path; andlogic means (182a+182b of FIG. 13A, or 230a+230b of FIG. 14A), having afirst logic port (183 of FIG. 13A, or 224c of FIG. 14A) that isconnected to said effective output operator, having a second logic port(179a of FIG. 13A, or 226c of FIG. 14A) that is connected to saidcontrol port, and having a third logic port (179b of FIG. 13A, or 227cof FIG. 14A) that is adapted for connection to a fluid pressure, forestablishing fluid communication to said first logic port and to saideffective output operator from the one of the other two of said logicports having the higher fluid pressure therein, and for preventing fluidflow from said first logic port to the one of said two other logic portswith the lower fluid pressure therein.
 32. A load responsive hydraulicsystem (FIG. 3 or FIG. 12,+FIG. 1 or FIG. 15,+FIG. 14A) as claimed inclaim 31 in which said logic means comprises a three-port logic valve(230c of FIG. 14A.
 33. A load responsive hydraulic system (FIG. 3 orFIG. 12,+FIG. 1 or FIG. 15,+FIG. 13A) as claimed in claim 31 in whichsaid logic means comprises a first one-way flow valve (182a)communicating said control port (130 or 130g) to said effective outputoperator (28 or 56) and preventing reverse flow therebetween, and asecond one-way flow valve (182b) communicating said third logic port(179d) to said effective output operator in preventing reverse flowtherebetween.
 34. A load responsive hydraulic system (FIG. 3 or FIG.12,+FIG. 1 or FIG. 15) as claimed in claim 31 in which said systemincludes means for attenuating (160 of FIG. 1, 299 of FIG. 15, or 185 ofFIG. 13A) said higher fluid pressure applied to said effective outputoperator when said valving element means is in said stand-by position(FIG. 1, or FIG. 15).
 35. A load responsive hydraulic system (FIG. 3 orFIG. 12,+FIG. 1 or FIG. 15) as claimed in claim 34 in which saidattenuating means comprises a fourth fluid flow path (160 of FIG. 1, or299 of FIG. 15) that is established from said control port (130 or 130g)to said sump by said directional control valve (80 or 280) when saidvalving element means (94 or 284) is in said stand-by position (FIG. 1or FIG. 15).
 36. A load responsive hydraulic system (FIG. 3 or FIG.12,+FIG. 1 or FIG. 15,+FIG. 13A) as claimed in claim 34 in which saidattenuating means comprises a restrictor (185 of FIG. 13A) thatcommunicates said effective output operator (28 of FIG. 3, or 56 of FIG.12) to said sump (24f of FIG. 13A).
 37. A load responsive hydraulicsystem (FIG. 3 or FIG. 12,+FIG. 1 or FIG. 15) as claimed in claim 31 inwhich said valved signal means (128 or 238) includes second fluidrestrictor means (138a or 146a of FIG. 8, or 204a of FIG. 16, or 222 ofFIG. 17) for providing predetermined resistance to fluid flow from saidcontrol port (130 or 130g) to said first work port channel (86a, 294a,or 294b).
 38. A load responsive hydraulic system (FIG. 3 or FIG.12,+FIG. 1 or FIG. 15) of the type having a source (20 or 46) ofpressurized fluid that includes a pump (22 or 48) and a sump 24a or24b), having effective output means (26 or 60) that includes aneffective output operator (28 or 56) for control of the pressure andeffective output of said pump in response to a signal pressure appliedto said effective output operator, having a fluid actuated device (156)that includes first (158a) and second (158b) actuating ports, and havinga directional control valve (80 or 280) that includes a pressure inletchannel (92 or 296) connected to said source, that includes first (86aor 294a) and second (86b or 294b) work port channels operativelyconnected to respective ones of said actuating ports, that includesreturn port means (88 or 288) operatively connected to said sump, andthat includes movable valving element means (94 or 284) for establishingboth a first fluid flow path (162, or 344=346a+346b) from said pump tosaid first actuating port at the load actuating pressure of said deviceand a second fluid flow path (164 or 348) from said second actuatingport to said return port means when said valving element means is movedto a first operating position, for establishing both a third fluid flowpath from said pump to said second actuating port and a fourth fluidflow path from said first actuating port to said return port means whensaid valving element means is moved to a second operating position, andfor occluding all of said fluid flow paths when said valving elementmeans is moved to a stand-by position, the improvement whichcomprises:valved signal means (128 or 238), comprising a control port(130 or 130g), comprising first (134a or 258a) and second (134b or 308a)signal passages in said directional control valve that communicate withsaid movable valving element means, and comprising cooperating portions(106a+102+110a, or 318+314b+312c) of said valving element means, forestablishing a first restricted flow path portion (170 of FIGS. 8 & 13C,or 305 of FIGS. 14E & 16) from said control port to said first work portchannel after said second fluid flow path is established and foroccluding said first restricted flow path portion before said secondfluid flow path is occluded, for establishing a second restricted flowpath portion (168 of FIGS. 8 & 13C, or 303 of FIGS. 14E & 16) from saidpressure inlet channel to said control port after said first restrictedflow path portion is established and for occluding said secondrestricted flow path portion before said first restricted flow pathportion is occluded, for establishing a third restricted flow pathportion (171 of FIGS. 1 & 13C, or 311 of FIGS. 14E & 17) from saidcontrol port to said second work port channel after said fourth fluidflow path is established and for occluding said third restricted flowpath portion before said fourth fluid flow path is occluded, and forestablishing a fourth restricted flow path portion (169 of FIGS. 1 &13C, or 309 of FIGS. 14E & 17) from said pressure inlet channel to saidcontrol port and for occluding said fourth restricted flow path portionbefore said third restricted flow path portion is occluded; and means(36, 230a, etc.), being operatively connected to said control port andto said effective output operator, for applying said sensed fluidpressure to said effective output operator.
 39. A load responsivehydraulic system (FIG. 3 or FIG. 12,+FIG. 1 or FIG. 15) as claimed inclaim 38 in which said second restricted flow path portion (168 of FIGS.8 & 13C, or 303 of FIGS. 14E & 16) provides less restriction to fluidflow than said first restricted flow path portion (170 of FIGS. 8 & 13C,or 305 of FIGS. 14E & 16).
 40. A load responsive hydraulic system (FIG.3 or FIG. 12,+FIG. 1) as claimed in claim 38 in which said first (170 ofFIGS. 8 & 13C) and fourth (169 of FIGS. 1 & 13C) restricted flow pathportions comprise opposite directions of fluid flow in a first passage(134a), and said second (168) and third (171) restricted flow pathportions comprise opposite directions of fluid flow in a second signalpassage (134b).
 41. A load responsive hydraulic system (FIG. 3 or FIG.12,+FIG. 1) as claimed in claim 40 in which said restrictions of saidfirst (170) and fourth (169) restricted flow path portions comprise afirst flow restrictor (138a), and said restriction of said second (168)and third (171) restricted flow path portions comprise a second flowrestrictor (138b).
 42. A load responsive hydraulic system (FIG. 3 orFIG. 12,+FIG. 1) as claimed in claim 41 in which one of said passages(134a or 134b) includes a one-way flow and reverse flow restrictor valve(140a or 140b) therein; andsaid restriction of one (170 or 171) of saidrestricted flow path portions includes said one-way flow and reverseflow restrictor valve.
 43. A load responsive hydraulic system (FIG. 3 orFIG. 12,+FIG. 1 or FIG. 15) of the type having a source (20 or 46) ofpressurized fluid that includes a pump (22 or 48) and a sump (24a or24b), having effective output means (26 or 60) that includes aneffective output operator (28 or 56) for control of the pressure andeffective output of said pump in response to a signal pressure appliedto said effective output operator, having a fluid actuated device (156)that includes first (158a) and second (158b) actuating ports, and havinga directional control valve (80 or 280) that includes a pressure inletchannel (92 or 296) connected to said source, that includes first (86aor 294a) and second (86b or 294b) work port channels operativelyconnected to respective ones of said actuating ports, that includesreturn port means (88 or 288) operatively connected to said sump, andthat includes movable valving element means (94 or 284) for establishingboth a first fluid flow path (162, or 344=346a+346b) from said pump tosaid first actuating port at the load actuating pressure of said deviceand a second fluid flow path (164 or 348) from said second actuatingport to said return port means when said valving element means is movedto an operating position, and for occluding said first and second fluidflow paths when said valving element means is moved to a stand-byposition, the improvement which comprises:valved signal means (238),comprising first (258a or 258b) and second (308a or 308b) signalpassages, comprising a one-way flow valve (204a or 206) in said secondsignal passage, and comprising a control port (130g) for establishing afirst flow path portion (303 of FIG. 16, or 309 of FIG. 17) thatcommunicates said pressure inlet channel to said control port after saidsecond fluid flow path is established, for providing a second flow pathportion (305 of FIG. 16, or 311 of FIG. 17) from said control port tosaid first work port channel through said one-way flow valve, forpreventing fluid flow from said first work port channel to said controlport through said second flow path portion, for providing a fluidrestriction (210a of FIG. 16, or 210b or 318 of FIG. 17) in said firstflow path portion, and for occluding said first flow path portion beforesaid occlusion of said second fluid flow path; and means, beingoperatively connected to said control port and to said effective outputoperator, for communicating fluid pressure from said control port tosaid effective output operator.
 44. A load responsive hydraulic system(FIG. 3 or FIG. 12,+FIG. 15) as claimed in claim 43 in which saidone-way flow means comprises a check valve (206 of FIG. 17).
 45. A loadresponsive hydraulic system (FIG. 3 or FIG. 12,+FIG. 15) as claimed inclaim 43 in which said one-way flow means comprises a relief valve (204aof FIG. 16).
 46. A load responsive hydraulic system (FIG. 3 or FIG.12,+FIG. 15) as claimed in claim 43 in which said valved signal means(238) includes second fluid restriction means (204a or 222) forproviding a predetermined resistance to fluid flow from said controlport (130g) to said first work port channel (294a or 294b).
 47. A loadresponsive hydraulic system (FIG. 3 or FIG. 12,+FIG. 15) as claimed inclaim 46 in which said second fluid restriction means comprises a fixedconductance restrictor (222).
 48. A load responsive hydraulic system(FIG. 3 or FIG. 12,+FIG. 15) as claimed in claim 46 in which both saidsecond fluid restriction means and said one-way flow means comprise aresiliently biased restrictor (204a).
 49. A load responsive hydraulicsystem (FIG. 3 or FIG. 12,+FIG. 1 or FIG. 15) of the type having asource (20 or 46) of pressurized fluid that includes a pump (22 or 48)and a sump (24a or 24b), having effective output means (26 or 60) thatincludes an effective output operator (28 or 56) for control of thepressure and effective output of said pump in response to a signalpressure applied to said effective output operator, having a fluidactuated device (156) that includes first (158a) and second (158b)actuating ports, and having a directional control valve (80 or 280) thatincludes a pressure inlet channel (92 or 296) connected to said source,that includes first (86a or 294a) and second (86b or 294b) work portchannels operatively connected to respective ones of said actuatingports, that includes return port means (88 or 288) operatively connectedto said sump, and that includes movable valving element means (94 of284) for establishing both a first fluid flow path (162, or344=346a+346b) from said pump to said first actuating port at the loadactuating pressure of said device and a second fluid flow path (164 or348) from said second actuating port to said return port means when saidvalving element means is moved to a first operating position, forestablishing both a third fluid flow path from said pump to said secondactuating port and a fourth fluid flow path from said first actuatingport to said return port means when said valving element means is movedto a second operating position, and for occluding all of said fluid flowpaths when said valving element means is moved to a standby position,the improvement which comprises:valved signal means (238), comprising alogic valve (256) that includes an unvalved logic port (271), thatincludes first (270a) and second (270b) valved logic ports, and thatincludes a shuttle (268), comprising a control port (130g) that isconnected to said unvalved logic port, comprising a first signal passage(308a) that interconnects said first valved logic port and said firstwork port channel, comprising a first one-way flow valve (204a) that isinterposed into said first signal passage, comprising a second signalpassage (308b) that interconnects said second valved logic port and saidsecond work port channel, and comprising a second one-way flow valve(206) that is interposed into said second signal passage, forestablishing a first restricted flow path portion (303 of FIG. 16) thatcommunicates said pressure inlet channel to said control port after saidsecond fluid flow path has been established, for establishing a firstone-way flow path portion (305 of FIG. 16) from said first restrictedflow path portion to said first work port channel, for occluding saidfirst restricted flow path portion before said occluding of said secondfluid flow path, for establishing a second restricted flow path portion(309 of FIG. 17) that communicates said pressure inlet channel to saidcontrol port after said fourth fluid flow path has been established, forestablishing a second one-way flow path portion (311 of FIG. 17) fromsaid second restricted flow path portion to said second work portchannel, and for occluding said second restricted flow path portionbefore said occluding of said fourth fluid flow path; and means (36),being operatively connected to said control port and to said effectiveoutput operator, for communicating fluid pressure from said control portto said effective output operator.
 50. A load responsive hydraulicsystem (FIG. 3 or FIG. 12,+FIG. 15) as claimed in claim 49 in which saiddirectional control valve (280) includes a body (282) having a spoolbore (286);said pressure inlet channel (296), said return port means(290+292a+292b) and one (294b) of said work port channels intercept saidspool bore in spaced-apart locations; said movable valving element meanscomprises a valve spool (284) having three land portions (312a, 312b,and 213c) that are spaced-apart by respective ones of two (314a or 314b)reduced cross-section portions; and said valved signal means and saidestablishing of one of said restricted flow path portions (303 of FIG.16, or 309 of FIG. 17) thereof comprises one of said signal passages(258a or 258b) intercepting said spool bore.
 51. A load responsivehydraulic system (FIG. 3 or FIG. 12,+FIG. 15) as claimed in claim 50 inwhich said intercepting means comprises an elongated circumferentialgroove (298) that divides said spool bore (286) into a first boreportion (350) that is intermediate of said pressure inlet channel (296)and said circumferential groove (298), and a second bore portion (351)that is proximal to said circumferential groove and distal from saidpressure inlet channel;said circumferential groove has a longer lengththan that of said second land portion; and said establishing of saidfirst fluid flow path (344=346a+346b) comprises positioning the centerone (312b) of said three land portions within said elongatedcircumferential groove when said valve spool is in said operatingposition (FIG. 16), and communicating said pressure inlet channel withsaid second bore portion by said second (314b) and first (314a) reducedcross-section portions.
 52. A load responsive hydraulic system (FIG. 3or FIG. 12,+FIG. 15) as claimed in claim 51 in which said valved signalmeans (238) comprises longitudinally disposed hole means(328=330+332+334) in said valve spool for establishing an attenuationflow path (299) from said elongated circumferential groove (298) to saidreturn port means (288=290+292a+292b) when said movable valving element(284) is in said stand-by position (FIG. 15) and for occluding saidattenuation flow path before said first (344=346a+346b) fluid flow pathis established.
 53. A load responsive hydraulic system (FIG. 3 or FIG.12,+FIG. 15) as claimed in claim 50 in which said valved signal means(238) and said communicating of said second restricted flow path portion(309 of FIG. 17) thereof to said control port (130g) comprisesconnecting said second restricted flow path portion to said unvalvedlogic port (271 via chamber 274) of said logic valve (256).
 54. A loadresponsive hydraulic system (FIG. 3 or FIG. 12,+FIG. 15) as claimed inclaim 53 in which said logic valve (256) includes a shuttle (268), andmeans (272) for resiliently urging said shuttle into flow occludingengagement with one (270a) of said valved logic ports.